Gray iron

ABSTRACT

High strength low hardness gray iron consisting essentially of about 1 - 3 percent aluminum, 2 - 4 percent carbon, up to 1% silicon and the balance iron, said gray iron having been inoculated with a minimum of 0.3 percent of an inoculant alloy, the active inoculant of which is selected from the group consisting of calcium, barium and strontium.

United States Patent [191 Defranco et a1.

GRAY IRON Inventors: Charles Defranco, Zele; Jan Van Eeghem, Deurle,both of Belgium Centre de Recherches Scientifiques et llndustrie desFabrications Metalliques, en abrege, C.R.I.F., Brussels, Belgium Filed:Dec. 15, 1971 Appl. No.: 208,489

Related U.S. Application Data Continuation of Ser. No. 797,622, Feb. 7,1969, abandoned.

Assignee:

Foreign Application Priority Data Kglmm [451 Mar. 19, 1974 [56]References Cited UNITED STATES PATENTS 2,793,114 5/1957 Moore 75/1302,885,284 5/1959 Moore 75/124 1,515,244 11/1924 Early 75/130 R X2,134,905 11/1938 Bampfylde 75/130 R X 2,950,187 8/1960 Ototani 75/124 X3,433,685 3/1969 Albertzart 148/35 Primary ExaminerL. Dewayne Rutledgefifi ifllii miflf fila M; Pari V, Attorney, Agent, or F irm-Hubbell,Cohen & Stiefel; Sheldon Palmer [57] ABSTRACT High strength low hardnessgray iron consisting essentially of about '1 3 percent aluminum, 2 4percent 1 carbon, up to 1% silicon and the balance iron, said gray ironhaving been inoculated with a minimum of 0.3 percent of an inoculantalloy, the active inoculant of which is selected from the groupconsisting of calcium, barium and strontium.

12 Claims, 3 Drawing Figures as l f I 2a PATENTED MAR 1 9 I974 SHEU 1[IF 2 Kg/mm FIG/i.

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IIVUENTORJ mamas psrnwao .m/v vmv E56 HEM GRAY IRON CROSS-REFERENCE TORELATED APPLICA- TIONS This application is a continuation ofapplication, Ser. No. 797,622, filed Feb. 7, 1969, now abandoned.

The present invention relates to gray iron.

The gray irons actually known as high strength gray irons with lamellargraphite have relatively low carbon (2.6 to 3.2 percent) and silicon (lto 1.5 percent) contents.

The tensile strength of these known irons, measured on a 30mm standardtest-bar rarely exceeds 45 kgf/mm whereas their Brinell hardness may beas high as 320 Brinell.

To attain this high strength, it is generally necessary to add costlyalloying elements such as copper, nickel,

molybdenum and/or chromium, and to subsequently 1 inoculate the liquidiron.

Furthermore, as a result of their low carbon and silicon contents theseknown high strength cast irons also present the disadvantage of a ratherhigh tendency to white chilling. The danger of unmachinable white ironformation thus increases with the decreasing wall thickness of thecasting.

Furthermore due to their high hardness, the machin- V ability of theknown high strength cast irons is rather poor.

The production of cast iron based on iron carbon and aluminum, withlittle or no silicon was proposed more than 30 years ago.

However, such ironswere cast in the non-inoculated state, and theirproperties were inferior to those of the classical silicon cast irons.

Present knowledge concerning the inoculation mechanism enables one togive a plausible explanation to this phenomenon.

Indeed, due to the high deoxidizing power of aluminum the oxygen contentof high aluminum irons, whether it is dissolved as FeO particles orcombined with silicon as SiO inclusions, is almost negligible. Thismeans that silicon particles, which act as natural nuclei in normal graysilicon-bearing irons are absent in high aluminum cast irons, and thus,these known but non-inoculated cast irons have a high chilling tendencyand tensile properties which are not superior to, and may even beinferior to those of silicon irons.

The present invention is a new and improved alloy, having propertieswhich are not present in irons where aluminum is used with medium orhigh silicon contents (which are normal in classical silicon irons) norin irons where high silicon contents are used without aluminum even wheninoculated with an alloy containing calcium, barium or strontium. Forthis purpose, the cast iron according to the invention is characterizedby the fact, that on the one hand it contains aluminum as a graphitizingelement, and on the other hand it is inoculated.

The tensile strength of the irons according to the invention varies, forirons with lamellar graphite, be tween 35 and 70 kgf/mm as a function ofwallthickness and carbon and aluminum contents; their tendency tochilling is almost non-existent.

Belgian patent 563,443 of Dec. 12, I957 discloses a ferrous alloy whichis obtained by simultaneous addition of manganese and aluminum in orderto improve the wear and heat'resistance of the iron. The properties ofthis known iron are considerably different from those of the ironaccording to the present invention, as

will appear below from a more detailed description of the present iron.

US. Pat. No. 2,662,820 of June 30, 1950 suggests the addition ofaluminum in the course of elaboration of a gray iron. It must be pointedout however, that this patent concerns the production of a classicalgray iron with spheroidal graphite, the purpose of the aluminum being toextend the duration of the effect of the nodulizing agent.

According to an advantageous embodiment of the present invention theuseful and economical range of the aluminum content lies between 1 and 3percent.

The silicon content of the cast irons according to the present inventionshould preferably and advantageously be lower than 1 percent.

In a particular embodiment of the invention, the silicon content iszero. Indeed, as a further advantage of the present invention, theselected from the group consisting of barium and strontium isincorporated in the molten iron by an aluminum containing bearer.

Other details and particularities of the present invention will beapparent from the description given below, by way of non-limitativeexample, of several embodiments of the invention, with reference to thedrawings which show comparative graphs of the physical properties of thecast iron according to this invention, wherein FIG. 1 shows tensilestrength plotted against carbon content, FIG. 2 shows tensile strengthplotted against silicon content, and FIG. 3 shows tensile strengthplotted against Brinell hardness.

The graph of FIG. 1 shows the variation of tensile strength in 30 mm-diameter test bars (ordinate), determined as a function of carboncontent (abscissa) on irons containing respectively an average aluminiumcontent of 1.8 percent (curve 1) or 2.5 percent (curve 2) and inoculatedby addition of 1% SiCa.

The straight dotted line, 3, in FIG. 1, represents the theoreticaltensile strength of classical irons containing 1.5 percent silicon.

It is seen therefrom that at the same level of carbon content, thestrengths of the aluminum irons inoculated with l% SiCa, exceed by 10 to15 kgf/mm the strengths of the classical irons containing 1.5 percentsilicon.

According to an advantageous embodiment of the present invention, theuseful and economical range of the aluminum contents lies between I and3 percent.

FIG. 2 shows the influence of increasing silicon contents (abscissa) onthe tensile strength (ordinate) of inoeula ted aluminum bearing ironcast intest-bars of 3 different diameters.

Curve 4 relates to 30 mm -diameter test bars, curve 5 to 20 ram-diametertest bars and curve 6 to 12 m ndiameter test bars.

It can be seen that the influence of silicon is slight between 0.4 and0.8 percent, that the optimum value is about 0.75 percent and that inamounts over 0.9 percent silicon the tensile strength drops veryquickly.

The silicon content of the irons according to the present inventionshould therefore preferably be lower than 1 percent.

According to a particular embodiment of the present invention, thesilicon content of the iron as graphitizing element may even be zero, inwhich case the silicon is replaced totally by aluminum.

The influence of increasing manganese, sulfur and phosphorus contents onthe properties of a base iron TAELE 1 Curve 7 of HG. 3 shows therelationship between tensile strength (ordinate) and Brinell hardness(ablnfluence of Mn, S and P on the mechanical properties of aluminumcast iron Cast Chill R kgllmm Impact depth modulus iron in mm 45 30 mm46 mm 12 mm HB d: mm kgfcm/cm -cwflc. isw W W c- -W o .025 1 48.6 52 25612.2 .038 2 46.5 51.2 51.8 2 2 4 lg l B .051 4 49.2 51.2 53.5 249 10.9.079 5 43.6 48 50 252 11.6

These results show that manganese increases the chifi depth anddecreases both the tensile strength and the impact modulus, particularlywhen the manganese content exceeds 0.6 percent.

Sulfur increases the chill depth and decreases both the tensile strengthand the impact modulus.

Phosphorus has no influence on chill depth but considerably decreasesthe impact modulus.

It is thus advantageous to limit the manganese, sulfur and phosphoruscontents respectively to the following maximum values: 0.7 percent forMn; 0.05 percent for S and 0.1 percent for P.

Due to the absence of natural nuclei and in spite of the graphitizingeffect of the aluminum, the tendency to ledeburitic solidification ofthe non-inoculated castirons according to the invention is veryimportant.

The chill depth of the non-inoculated cast irons varies generallybetween 20 mm and total chill, although it becomes almost non-ex'istant(O2 mm) after inoculation.

However, to obtain this result, the amount of inoculating alloy added tothe cast iron according to the invention must be more greater than thatused for the inoculation of conventional silicon cast irons.

Indeed, while the conventional cast irons are generally inoculated with0.1 to 0.3 percent of an inoculant, for instance SiCa, the cast ironsaccording to the invention must be inoculated with at least 0.3% SiCa.

Although the properties increase with the amount of added inoculant, itis not justified economically to use more than 2% SiCa. I

It must be mentioned that it is not indispensable that the inoculantcontain silicon as the bearer of the active inoculating element. On thecontrary, in order to avoid the introduction of silicon in the iron, andthe accumu-- lation of this element by using foundry returns, it isadvantageous to inoculate with alloys of the Fe-Al-Ca type. which do notcontain silicon, and which have been specially developed for thispurpose.

scissa) of 5655156553011. The Ffikifr'cie are the results obtained withirons containing 1.8 percent aluminum, whereas the crosses represent theresults obtained on irons containing 2.5 percent aluminum, all testshaving been performed on cast irons inoculated with 1% SiCa and cast in30 mm-diameter bars.

For comparison purposes with conventional silicon cast irons, thestraight dotted line 8 gives the theoretical relation according to theformula HB 4.3 R,, where HE is the Brinell Hardness, and

R, is the Tensile Strength.

The black circles represent the scarce quantitative data given in theliterature for conventional high strength gray irons.

As seen from FIG. 3, with the same level of tensile strength, theBrinell hardness of the aluminum cast iron is on the average 50 to 60Brinell units lower than that of the conventional silicon cast irons.

In spite of the high strengths, the hardness of the cast irons accordingto the invention is relatively low, which results in machinability whichis comparable to, or even betterthan that of the silicon cast irons.

The cast irons according to the present invention also have theadvantage of being made from inexpensive raw materials.

The new cast irons are particularly suited to produce high strengthcastings and thin-walled castings which have to be machined.

The aluminum contained in these cast irons prevents any mold-metalreactions so that sand adherence is almost unexisting.

The skin of the castings of aluminum cast iron is smoother than the skinof the usual castings of silicon cast iron, which allows a considerablereduction of cleaning costs. 7

A particularly interesting area of application of the new cast irons isin casting in metal molds.

The castings in conventional silicon irons, cast in metal molds mustgenerally be heat-treated to decompose the carbides which are formedduring the rapid cooling in the metal mold.

It has been shown experimentally that due to the very low tendency tochilling of the irons according to the present invention, the castingsmade in metal molds with these irons, do not have to be heat-treatedafterwards.

Two non-limitative examples of the composition of cast irons accordingto the invention, untreated for nodulizing and cast in bars are givenbelow.

The hardness and strength tables of in Example 1 give the comparativeresults of tests for an iron according to the invention which has beeninoculated, the silicon content being the sum of the silicon content ofthe base materials and the silicon content added to the iron as acomponent of the inoculant, and for the noninoculated base iron, thesilicon content of the latter being the silicon content of the base n atet ials.

i i M lli- Chemical composition:

l. A high strength low hardness gray iron consisting essentially ofabout 1 3 percent aluminum, 2 4 percent carbon, up to 1 percent siliconand the balance iron, said gray iron having been innoculated with l to 2percent of an inoculant alloy, the active inoculant of which is selectedfrom the group consisting of calcium, barium and strontium, said activeinoculant being preseltia P'EfiUQljEEF! emqqn s ivs, F L 3 b?non-inoculated base iron 2.90% C; 0.09% Si; 1.85% Al inoculated iron2.70% C; 0.35% Si; 1.85% Al inoculation with SiCa: 1%

Tensile strength in kgf/mm 30mm 20mm 12mmnon-inoculinoculnon-inoculinoculnoninocu1- inoculated ated ated atedated ated 24.7 50.2 38.9 52.6 white iron 57.9

non-inoculated inoculated chill depth in mm: 40 2 impact modulus:kgfcm/cm: (da mm) 5.6 13.5

Brinell Hardness 4530mm 20mm 12mmnon-inoculinoculnon-inoculinoculnon-inoculinoculated ated ated ated atedated 246 234 295 256 white iron 280 EXAMPLE 2 Brinell Hardness of the ascast alloy by about 50 Brinell In this example an iron inoculated with1% Fe-Al- Ca has been added flor comparison.

units.

1A h en t 10W a ness re rs sensistin Chemical composition non-inoculated3.18 0.15 0.45 0.042 0.040 2.53 inoculated with SiCa 3.02 0.77 0.440.042 0.030 2.53 inoculated with Fe-Al-Ca 3.10 0.12 0.45 0.041 0.0312.85 (Fe: Al: 40%; Ca: 20%) Properties 30 mm 4b 20 mm d) 12 mm nqn-ino-SiCa FeAl non-ino- SiCa FeAl non-ino- SiCa FeAl culated Ca culated Caculated Ca Tensile strength 40.1 47.6 49.8 42 51.8 53.5 43.2 53.3 55.1kgf/mm Brinell Hardness 239 241 245 272 285 278 288 302 302non-inoculated SiCa FeAlCa Chill depth in mm: 20 0.5 0.5

essentially of about 1 3 percent aluminum, 2 4 percent carbon, up to 1percent silicon, up to 0.7 percent manganese, and the balance iron, saidgray iron having been inoculated with l to 2 percent of an inoculantalloy, the active inoculant of which is selected from the groupconsisting of calcium, barium and strontium, said active inoculant beingpresent in the alloy in an amount effective to reduce the BrinellHardness of the as cast alloy by about 50 Brinell units.

3. A high strength low hardness gray iron consisting essentially ofabout 1 3 percent aluminum, 2 4 percent carbon, up to 1 percent silicon,up to 0.7 percent manganese, up to 0.05 percent sulfur, up to 0.1percent phosphorus, and the balance iron, said gray iron having beeninoculated with l to 2 percent of an inoculant alloy, the activeinoculant of which is selected from the group consisting of calcium,barium and strontium, said active inoculant being present in the alloyin an amount effective to reduce the Brinell Hardness of the as castalloy by about 50 Brinell units.

4. A high strength low hardness gray iron having a flake graphitestructure and consisting essentially of about 1 3 percent aluminum, 2 4percent carbon, up to 1 percent silicon and the balance iron, said grayiron having been inoculated with l to 2 percent of an inoculant alloy,the active inoculant of which is selected from the group consisting ofcalcium, barium and strontium, said active inoculant being present inthe alloy in an amount effective to reduce the Brinell Hardness of theas cast alloy by about 50 Brinell units.

5. A high strength low hardness gray iron consisting essentially ofabout 1 3 percent aluminum, 2 4 percent carbon, upto 1 percent siliconand the balance iron, said gray iron having been inoculated with l to 2percent of an inoculant alloy selected from the group consisting of SiCaconsisting essentially of about 33 percent calcium and the balance beingsilicon and FeAlCa consisting essentially of about 40 percent iron, 40percent aluminum and percent calcium.

6. A high strength low hardness gray iron consisting essentially ofabout 1 3 percent aluminum, 2 4 percent carbon, up to 1 percent silicon,up to 0.7 percent manganese and the balance iron, said gray iron havingbeen inoculated with l to 2 percent ofan inoculant alloy selected fromthe group consisting of SiCa consisting essentially of about 33 percentcalcium and the balance being silicon and FeAlCa consisting essentiallyof about 40 percent iron, 40 percent aluminum and 20 percent calcium.

7. A high strength low hardness gray iron consisting essentially ofabout 1 3 percent aluminum, 2 4 percent carbon, up to l percent silicon,up to 0.7 percent manganese, up to 0.05 percent sulfur, up to 0.1percent phosphorus and the balance iron, said gray iron having beeninoculated with l to 2 percent of an inoculant alloy selected from thegroup consisting of SiCa consisting essentially of about 33 percentcalcium and the balance being silicon and FeAlCa consisting essentiallyof about 40 percent iron, 40 percent aluminum and 20 percent calcium.

8. A high strength low hardness gray iron having a flake graphitestructure and consisting essentially of about 1 3 percent aluminum, 2 4percent carbon, up to 1 percent silicon and the balance iron, said grayiron having been inoculated with l to 2 percent of an inoculant alloyselected from the group consisting of SiCa consisting essentially ofabout 33 percent calcium and the balance being silicon and FeAlCaconsisting essentially of about 40 percent iron, 40 percent aluminum and20 percent calcium.

9. In a cast gray iron article having a chill depth in mm. of betweenabout 0.5 and 2, said article consisting essentially of about I 3percent aluminum, 2 4 percent carbon, up to 1 percent silicon and thebalance iron, said gray iron having been inoculated with 1 to 2 percentof an inoculant alloy, the active inoculant of which is selected fromthe group consisting of calcium, barium and strontium, said activeinoculant being present in the alloy in an amount effective to reducethe Brinell Hardness of the as cast alloy by about 50 Brinell units.

10. In a cast gray iron article having a chill depth in mm. of betweenabout 0.5 and 2, said article consisting essentially of about 1 3percent aluminum, 2 4 percent carbon, up to 1 percent silicon, up to 0.7percent manganese, and the balance iron, said gray iron having beeninoculated with 1 to 2 perce of an inocu- Ent alloy, the activeinoculant brivifihi elected from the group consisting of calcium, bariumand strontium, said active inoculant being present in the alloy in anamount effective to reduce the Brinell Hardness of the as cast alloy byabout 50 Brinell units.

11. In a cast gray iron article having a chill depth in mm. of betweenabout 0.5 and 2, said article consisting essentially of about 1 3percent aluminum, 2 4 percent carbon, up to 1 percent silicon, up to 0.7percent manganese, up to 0.05 percent sulfur, up to 0.1 percentphosphorus, and the balance iron, said gray iron having been inoculatedwith l to 2 percent of an inoculant alloy, the active inoculant of whichis selected from the group consisting of calcium, barium and strontium,said active inoculant being present in the alloy in an amount effectiveto reduce the Brinell Hardness of the as cast alloy by about 50 Brinellunits.

12. In a cast gray iron article having a flake graphite structure and achill depth in mm. of between about 0.5 and 2, said article consistingessentially of about 1 3 percent aluminum, 2 4 percent carbon, up to lpercent silicon and the balance iron, said gray iron having beeninoculated with l to 2 percent of an inoculant alloy, the activeinoculant of which is selected from the group consisting of calcium,barium and strontium, said active inoculant being present in the alloyin an amount effective to reduce the Brinell Hardness of the as castalloy by about 50 Brinell units.

Patent No.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 3,798,027 DatedMarch 19, 1974 Charles Defrancq et a1. Inventor(s) It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Title page, left side alongside the word "inventorsz' "Charles Defranco"should read Charles Defrancq alongside the word "Assignee"; "Centre deRecherches Scientifiques et l'lndustrie des Fabrications Metalliques,

en abrege', C.R.I.F.," should read Centre de Recherches Scientifiques etTechniques d l'Industrie des Fabrications metalliques, en abrege,C.R.I.F., Column 2, line l8, "the selected" should read the activeinoculating element selected Column 2, line 19, "of barium andstrontium" should read of calcium, barium and strontium Column 5,

line 13, "tables of in" should read tables in Column 5 v Example 2,"Tensile strength kgf/mm" should read Tensile 2 strength kgf/mm Column6, line 2, "beside" should read besides Column 6, line 19, claim 1:"innoculated" should read inoculated Signed and' sealed this 17th day ofSeptember 1974.-

(SEAL) Attest: I v

C. MARSHALL DANN MCCOY GIBSON Commissioner of Patents Att sting Officer

2. A high strength low hardness gray iron consisting essentially ofabout 1 - 3 percent aluminum, 2 - 4 percent carbon, up to 1 percentsilicon, up to 0.7 percent manganese, and the balance iron, said grayiron having been inoculated with 1 to 2 percent of an inoculant alloy,the active inoculant of which is selected from the group consisting ofcalcium, barium and strontium, said active inoculant being present inthe alloy in an amount effective to reduce the Brinell Hardness of theas cast alloy by about 50 Brinell units.
 3. A high strength low hardnessgray iron consisting essentially of about 1 - 3 percent aluminum, 2 - 4percent carbon, up to 1 percent silicon, up to 0.7 percent manganese, upto 0.05 percent sulfur, up to 0.1 percent phosphorus, and the balanceiron, said gray iron having been inoculated with 1 to 2 percent of aninoculant alloy, the active inoculant of which is selected from thegroup consisting of calcium, barium and strontium, said active inoculantbeing present in the alloy in an amount effective to reduce the BrinellHardness of the as cast alloy by about 50 Brinell units.
 4. A highstrength low hardness gray iron having a flake graphite structure andconsisting essentially of about 1 - 3 percent aluminum, 2 - 4 percentcarbon, up to 1 percent silicon and the balance iron, said gray ironhaving been inoculated with 1 to 2 percent of an inoculant alloy, theactive inoculant of which is selected from the group consisting ofcalcium, barium and strontium, said active inoculant being present inthe alloy in an amount effective to reduce the Brinell Hardness of theas cast alloy by about 50 Brinell units.
 5. A high strength low hardnessgray iron consisting essentially of about 1 - 3 percent aluminum, 2 - 4percent carbon, up to 1 percent silicon and the balance iron, said grayiron having been inoculated with 1 to 2 percent of an inoculant alloyselected from the group consisting of SiCa consisting essentially ofabout 33 percent calcium and the balance being silicon and FeAlCaconsisting essentially of about 40 percent iron, 40 percent aluminum and20 percent calcium.
 6. A high strength low hardness gray iron consIstingessentially of about 1 - 3 percent aluminum, 2 - 4 percent carbon, up to1 percent silicon, up to 0.7 percent manganese and the balance iron,said gray iron having been inoculated with 1 to 2 percent of aninoculant alloy selected from the group consisting of SiCa consistingessentially of about 33 percent calcium and the balance being siliconand FeAlCa consisting essentially of about 40 percent iron, 40 percentaluminum and 20 percent calcium.
 7. A high strength low hardness grayiron consisting essentially of about 1 - 3 percent aluminum, 2 - 4percent carbon, up to 1 percent silicon, up to 0.7 percent manganese, upto 0.05 percent sulfur, up to 0.1 percent phosphorus and the balanceiron, said gray iron having been inoculated with 1 to 2 percent of aninoculant alloy selected from the group consisting of SiCa consistingessentially of about 33 percent calcium and the balance being siliconand FeAlCa consisting essentially of about 40 percent iron, 40 percentaluminum and 20 percent calcium.
 8. A high strength low hardness grayiron having a flake graphite structure and consisting essentially ofabout 1 - 3 percent aluminum, 2 - 4 percent carbon, up to 1 percentsilicon and the balance iron, said gray iron having been inoculated with1 to 2 percent of an inoculant alloy selected from the group consistingof SiCa consisting essentially of about 33 percent calcium and thebalance being silicon and FeAlCa consisting essentially of about 40percent iron, 40 percent aluminum and 20 percent calcium.
 9. In a castgray iron article having a chill depth in mm. of between about 0.5 and2, said article consisting essentially of about 1 - 3 percent aluminum,2 - 4 percent carbon, up to 1 percent silicon and the balance iron, saidgray iron having been inoculated with 1 to 2 percent of an inoculantalloy, the active inoculant of which is selected from the groupconsisting of calcium, barium and strontium, said active inoculant beingpresent in the alloy in an amount effective to reduce the BrinellHardness of the as cast alloy by about 50 Brinell units.
 10. In a castgray iron article having a chill depth in mm. of between about 0.5 and2, said article consisting essentially of about 1 - 3 percent aluminum,2 - 4 percent carbon, up to 1 percent silicon, up to 0.7 percentmanganese, and the balance iron, said gray iron having been inoculatedwith 1 to 2 percent of an inoculant alloy, the active inoculant of whichis selected from the group consisting of calcium, barium and strontium,said active inoculant being present in the alloy in an amount effectiveto reduce the Brinell Hardness of the as cast alloy by about 50 Brinellunits.
 11. In a cast gray iron article having a chill depth in mm. ofbetween about 0.5 and 2, said article consisting essentially of about1 - 3 percent aluminum, 2 - 4 percent carbon, up to 1 percent silicon,up to 0.7 percent manganese, up to 0.05 percent sulfur, up to 0.1percent phosphorus, and the balance iron, said gray iron having beeninoculated with 1 to 2 percent of an inoculant alloy, the activeinoculant of which is selected from the group consisting of calcium,barium and strontium, said active inoculant being present in the alloyin an amount effective to reduce the Brinell Hardness of the as castalloy by about 50 Brinell units.
 12. In a cast gray iron article havinga flake graphite structure and a chill depth in mm. of between about 0.5and 2, said article consisting essentially of about 1 - 3 percentaluminum, 2 - 4 percent carbon, up to 1 perceNt silicon and the balanceiron, said gray iron having been inoculated with 1 to 2 percent of aninoculant alloy, the active inoculant of which is selected from thegroup consisting of calcium, barium and strontium, said active inoculantbeing present in the alloy in an amount effective to reduce the BrinellHardness of the as cast alloy by about 50 Brinell units.